Fig 4 - available from: BMC Molecular and Cell Biology
This content is subject to copyright. Terms and conditions apply.
In human-rodent hybrid cells, human chromosomes are preferentially incorporated into micronuclei and replicated at a different time than the main nucleus. a FISH analysis performed 1 week after fusion of COLO 320DM-donor cells with CHO K1 acceptor cells, revealing that many Alu-positive human chromosomes were trapped in the micronuclei (arrows). Scale bar: 10 μm. b Frequencies of micronuclei containing human, hamster, or both types of chromosomes, based on scoring of more than 500 interphase nuclei at each time point. c-e BrdU 30 min pulse-labelling showing replication in both Alu-positive micronuclei and the main nucleus (c), the micronucleus only (d), or the cell nucleus only (e). Scale bars: 10 μm. f Frequencies of the replication events in the micronucleus and nucleus were calculated by examining the indicated number of total and Alu-positive micronuclei; data are summarised in the table. Shown is a typical result. Qualitatively identical results were obtained from 2 independent fusion experiments
Source publication
Background
Extrachromosomal acentric double minutes (DMs) contribute to human malignancy by carrying amplified oncogenes. Recent cancer genomics revealed that the pulverization of defined chromosome arms (chromothripsis) may generate DMs, however, nobody had actually generated DMs from chromosome arm in culture. Human chromosomes are lost in human-...
Contexts in source publication
Context 1
... human chromosome arms were actively lost 1 week after fusion, approximately 70% of the hybrid cells contained micronuclei. Importantly, most of the micronuclei were composed of Alu-positive human chromatids (Fig. 4a, b). The frequency of such micronuclei had decreased significantly by 4 weeks after the fusion, when most of the human chromosome arms had already been ...
Context 2
... detecting pulse-incorporated BrdU among nonsynchronous population, we compared the replication timing of Alu-positive micronuclei and the adjacent main nucleus at 10 days and 3 weeks after the cell fusion. The result revealed that a significant fraction of Alu-positive micronuclei replicated on a different time scale than the main nucleus ( Fig. 4c-f ). Such differential replication timing between the micronucleus and the nucleus might cause PCC of the micronuclear content, as reported ...
Similar publications
The progression of precancerous lesions to malignancy is often accompanied by increasing complexity of chromosomal alterations but how these alterations arise is poorly understood. Here we perform haplotype-specific analysis of chromosomal copy-number evolution in the progression of Barrett’s esophagus (BE) to esophageal adenocarcinoma (EAC) on mul...
Chromoanagenesis is a catastrophic event that involves localized chromosomal shattering and reorganization. In this study, we report a case of chromoanagenesis resulting from defective meiosis in the MEIOTIC ASYNAPTIC MUTANT 1 (asy1) background in Arabidopsis thaliana. We provide a detailed characterization of the genomic structure of this individu...
This article aims to summarize the current literature on genetic alterations related to tumors of the genitourinary tract. Novel associations have recently been reported between specific DNA alterations and genitourinary malignancies. The most common cause of chromosome 3p loss in clear cell renal cell carcinoma is a chromothripsis event, which con...
Background:
Chromothripsis is an event of genomic instability leading to complex chromosomal alterations in cancer. Frequent long-range chromatin interactions between transcription factors (TFs) and targets may promote extensive translocations and copy-number alterations in proximal contact regions through inappropriate DNA stitching. Although stu...
The gains and losses of DNA that emerge as a consequence of mitotic errors and chromosomal instability are prevalent in cancer. These copy number alterations contribute to cancer initiaition, progression and therapeutic resistance. Here, we present a conceptual framework for examining the patterns of copy number alterations in human cancer using wh...
Citations
... Moreover, specific kinds of cells tend to produce IR/MAR sequences. [26]. It should be noticed that multimerization of the episome/eccDNA containing the IR/MAR sequence creates larger and more complex DMs/ecDNAs [27]. ...
... It should be noticed that multimerization of the episome/eccDNA containing the IR/MAR sequence creates larger and more complex DMs/ecDNAs [27]. The process that causes the chromosomal arm to produce an initial tiny circle was addressed and replicated in culture by a model system [26]. In this system, chromothripsis occurs when a specific chromosome is abruptly fragmented, re-ligated, and then distributed by the rearrangement of numerous fragments [27]. ...
Cancer can be induced by a variety of possible causes, including tumor suppressor gene failure and proto-oncogene hyperactivation. Tumor-associated extrachromosomal circular DNA has been proposed to endanger human health and speed up the progression of cancer. The amplification of ecDNA has raised the oncogene copy number in numerous malignancies according to whole-genome sequencing on distinct cancer types. The unusual structure and function of ecDNA, and its potential role in understanding current cancer genome maps, make it a hotspot to study tumor pathogenesis and evolution. The discovery of the basic mechanisms of ecDNA in the emergence and growth of malignancies could lead researchers to develop new cancer therapies. Despite recent progress, different aspects of ecDNA require more investigation. We focused on the features, and analyzed the bio-genesis, and origin of ecDNA in this review, as well as its functions in neuroblastoma and glioma cancers.
... In several studies, chromothripsis was shown, directly or indirectly, to lead to ecDNA formation ( Figure 1B). When human chromosomes were pulverized in a process similar to chromothripsis in human-rodent hybrid cells, new stable ecDNAs were generated [54]. Furthermore, analysis of whole-genome sequencing (WGS) data from human cancers and chemotherapy-resistant clonal (1). ...
Extrachromosomal circular DNA (eccDNA) is a closed-circle, nuclear, nonplasmid DNA molecule found in all tested eukaryotes. eccDNA plays important roles in cancer pathogenesis, evolution of tumor heterogeneity, and therapeutic resistance. It is known under many names, including very large cancer-specific circular extrachromosomal DNA (ecDNA), which carries oncogenes and is often amplified in cancer cells. Our understanding of eccDNA has historically been limited and fragmented. To provide better a context of new and previous research on eccDNA, in this review we give an overview of the various names given to eccDNA at different times. We describe the different mechanisms for formation of eccDNA and the methods used to study eccDNA thus far. Finally, we explore the potential clinical value of eccDNA.
... This was consistent with the fact that natural DMs/ecDNA were a patchwork of sequences derived from several separate chromosome regions [46,47]. Such co-amplification of extrachromosomal circles drives the co-amplification of distantly located enhancer sequences together with the oncogene, thus enhancing the expression of oncogenes [48]. Furthermore, the efficiency of IR/MAR gene amplification varied significantly between normal and tumor cells as well as between the different tumor cell lines ( [43,49] our unpublished data). ...
Oncogene amplification is closely linked to the pathogenesis of a broad spectrum of human malignant tumors. The amplified genes localize either to the extrachromosomal circular DNA, which has been referred to as cytogenetically visible double minutes (DMs), or submicroscopic episome, or to the chromosomal homogeneously staining region (HSR). The extrachromosomal circle from a chromosome arm can initiate gene amplification, resulting in the formation of DMs or HSR, if it had a sequence element required for replication initiation (the replication initiation region/matrix attachment region; the IR/MAR), under a genetic background that permits gene amplification. In this article, the nature, intracellular behavior, generation, and contribution to cancer genome plasticity of such extrachromosomal circles are summarized and discussed by reviewing recent articles on these topics. Such studies are critical in the understanding and treating human cancer, and also for the production of recombinant proteins such as biopharmaceuticals by increasing the recombinant genes in the cells.
Glioblastoma evolution is facilitated by intratumour heterogeneity, which poses a major hurdle to effective treatment. Evidence indicates a key role for oncogene amplification on extrachromosomal DNA (ecDNA) in accelerating tumour evolution and thus resistance to treatment, particularly in glioblastomas. Oncogenes contained within ecDNA can reach high copy numbers and expression levels, and their unequal segregation can result in more rapid copy number changes in response to therapy than is possible through natural selection of intrachromosomal genomic loci. Notably, targeted therapies inhibiting oncogenic pathways have failed to improve glioblastoma outcomes. In this Perspective, we outline reasons for this disappointing lack of clinical translation and present the emerging evidence implicating ecDNA as an important driver of tumour evolution. Furthermore, we suggest that through detection of ecDNA, patient selection for clinical trials of novel agents can be optimized to include those most likely to benefit based on current understanding of resistance mechanisms. We discuss the challenges to successful translation of this approach, including accurate detection of ecDNA in tumour tissue with novel technologies, development of faithful preclinical models for predicting the efficacy of novel agents in the presence of ecDNA oncogenes, and understanding the mechanisms of ecDNA formation during cancer evolution and how they could be attenuated therapeutically. Finally, we evaluate the feasibility of routine ecDNA characterization in the clinic and how this process could be integrated with other methods of molecular stratification to maximize the potential for clinical translation of precision medicines.
